The present invention relates to a transportation system for performing intra-floor and inter-floor transportation of semi-processed products, in a manufacturing factory where a manufacturing line extends over a plurality of floors. More particularly, the present invention relates to a transportation system including a lift for inter-floor carriage, a carrier cart for intra-floor carriage, and a transit stocker for loading/unloading of an article to and from the lift.
A transportation system used in a manufacturing factory is disclosed in, for example, Japanese Unexamined Patent Publication No. Hei 5-19850, Japanese Unexamined Patent Publication No. Sho. 57-9614, and Japanese Unexamined Patent Publication No. Hei 11-95836.
The transportation system disclosed in Japanese Unexamined Patent Publication No. Hei 5-19850 includes a plurality of transporting stages for transferring an article from a carrier cart to a working machine, and each of the transporting stages includes a fault detector. A fault of the transporting stage is detected by the fault detector and stored in a controller for a carrier cart. When having received a carriage order from an order computer, the controller decides whether a transporting stage is broken down or not and, if the transporting stage is broken down, reports it to the order computer to thereby receive another instruction for changing the destination to another transporting stage. Thus, the transportation system disclosed in Japanese Unexamined Patent Publication No. Hei 5-19850 avoids a situation in which the carrier cart confusedly stops at a faulty transporting stage, thereby smoothing the operation of the carrier cart.
The transportation system disclosed in Japanese Unexamined Patent Publication No. Sho. 57-9614 includes a plurality of carrier elevators, a guide path along which a carrier cart travels, and guide branches for guiding the carrier cart to each of the elevators. Each elevator includes a sensor which, when it detects use of the elevator, opens a contact of a corresponding guide branch via a relay so that the carrier cart might not be guided to the elevator in use. Thus, the transportation system disclosed in Japanese Unexamined Patent Publication No. Sho. 57-9614 guides a carrier cart to an elevator not in use, to shorten waiting time for the elevator, thus improving the operation efficiency of the carrier cart.
Japanese Unexamined Patent Publication No. Hei 11-95836 discloses a transportation system in which a carrier cart travels along a loop-shaped track laid on a floor. A plurality of parts mounting stages and a plurality of parts dismounting stages are arranged along the track. To guide the carrier cart to these parts mounting/dismounting stages, the track is provided with branches. When the carrier cart has gone around the track and returned to its point of departure, it receives a radio signal of the data of the next round-travel path. The carrier cart then travels and branches according to this received path data to visit the parts mounting stage and the parts dismounting stage, and returns to the point of departure again. Thus, the transportation system disclosed in Japanese Unexamined Patent Publication No. Hei 11-95836 issues a radio signal of new path data each time the carrier cart goes around the track. Therefore, one carrier cart is efficiently utilized along a plurality of paths so that carrier carts exclusively provided for respective paths are not necessary. Moreover, it is unnecessary to re-write path data by hand.
The transportation system disclosed in Japanese Unexamined Patent Publication No. Hei 5-19850 carries the article to another stage in the case where a destination stage has broken down. However, the transportation system of this publication is provided with only one path for each stage, so that selection of an optimum path among a plurality of possible paths is not considered. Moreover, this publication is intended for a transportation system that carries an article within a single floor, and therefore, cannot be applied to a transportation system in which a carrier cart for carriage within a floor and a lift for carriage between floors are combined.
Likewise, the transportation system disclosed in Japanese Unexamined Patent Publication No. Sho. 57-9614 selects a vacant elevator among elevators having the equivalent functions. Therefore, the transportation system of this publication cannot decide which one of the elevators should be selected if their types differ from one another or if they are disposed far away from one another.
Further, in the transportation system disclosed in Japanese Unexamined Patent Publication No., Hei 11-95836 although a carriage route is supplied to the carrier cart each time the carrier cart travels around, each carriage route is previously assigned to a respective parts mounting stage and parts dismounting stage at which the carrier cart is to stop. Moreover, this publication is also directed to a transportation system that carries an article within a single floor, and therefore, cannot be applied to a transportation system in which a carrier cart for carriage within a floor and a lift for carriage between floors are combined.
Thus, the prior arts have not kept in mind such a transportation system in which a carrier for intra-floor carriage and a lift for inter-floor carriage are combined and a plurality of carriage routes can be selected for each pair of departure and destination points. Also, even in the case where a plurality of carriage facilities (transporting stages or elevators) are arranged in parallel with one another, a facility to be used is decided based only on whether it is usable and not on other factors, such as its operating rate or time required for carriage.
Accordingly, it is difficult to select an optimal carriage route even in a modem manufacturing factory in which a manufacturing line is provided over a plurality of floors to enable selecting a variety of carriage routes, so that, in practice, articles are carried along a carriage route determined beforehand. Therefore, at a specific one of transit stockers for transferring articles between, for example, a carrier cart and a lift, the articles might sometimes be concentrated, causing stagnation of carriages. Especially in an emergency where some of the carrier routes are rendered unusable due to a fault of any one of the facilities, carriages might severely stagnate. Furthermore, the operation status and the operating rate of the carriage facilities are not reflected in the selection of a carriage route, so that these facilities cannot be utilized effectively and carriage waiting time at each of these facilities tends to be elongated, thus resulting in uneconomical and inefficient carriage route selection in many cases.
In view of the above circumstances, it is an object of the present invention to provide a transportation system provided with a carrier cart for intra-floor carriage and a lift for inter-floor carriage in which carriage does not stagnate even upon occurrence of a fault of its facilities.
It is another object of the present invention to provide a transportation system equipped with a carrier cart for intra-floor carriage and a lift for inter-floor carriage that can utilize its carriage facilities effectively and shorten the carriage waiting time at each of the facilities, thus realizing efficient carriage.
A transportation system according to the present invention includes a plurality of lifts for inter-floor carriage, a carrier cart for intra-floor carriage and a transit stocker for loading/unloading of the lift. A lift to be used is decided based on at least one of operating or not of each lift, an operating rate of each lift, an inventory of each transit stocker, and a carriage queue for each lift.
Moreover, another transportation system according to the present invention includes a plurality of lifts for inter-floor carriage and a carrier cart for intra-floor carriage. A lift to be used decided based on operating rate of a carrier cart in each of the floor in such a manner that carriage distance is the smallest in the floor of the highest operating rate. Alternately, a lift to be used might be decided in such a manner that required time for carriage is the shortest in the floor of the highest operating rate.
According to the present invention, it is possible to select a carriage route based on the lift""s operation situation, stocker""s situation, and operating rate of the intra-floor transportation system to thereby select an optimal carriage route that has a short carriage waiting and a short carriage time.
Also, it is possible to prevent carriage from being stagnated at a lift or floor that has a low carriage capability. Further, it is possible to prevent occurrence of a carriage waiting owing to congested carriage at a specific lift or floor.
According to the present invention, therefore, it is possible to reduce the carriage waiting to thereby shorten the lead-time for finishing the product. Also, an effect of a possible fault on the carriage facilities can be reduced to a minimum.
These and other objects, advantages and features of the present invention will become more apparent from the following description and the accompanying drawings.